Optical recording media such as a write-once CD-R (Compact Disc-Recordable), DVD-R (Digital Versatile Disc-Recordable) and a rewritable CD-RW (CD-Re-writeable), DVD-RW (DVD-Re-writeable), Blu-ray and HD-DVD are being put into practical use or under further development. The optical discs may have a recording capacity ranging from hundreds of megabytes (MB) to more than 25 GB. Additionally, data can be recorded by a user on many current optical media. High-capacity data recording can be made with no loss of data quality due to remarkable improvement in performance of the large-capacity digital optical recording media and recording and reproducing apparatuses.
Additionally, a number of methods for generating labels on the upper surfaces of optical discs have recently been developed. One such method produces a color change in a layer of an optical disc by selectively exposing the layer to energy in the form of laser light that is absorbed by the layer and converted to heat. The heat effects an optical change in the label layer, thereby providing consumers with the ability to directly form identification labels on an optical disc. In order to controllably expose the label layer to laser light, an encoder often forms part of the label forming mechanism and codewheel features are employed on the optical disc to allow for measurement of disc position and rotational velocity. Recordable discs with this capability are commercially known as LightScribe discs.